code: def test_get_index_map(self):
      psdf = ps.DataFrame(
          {"year": [2015, 2016], "month": [2, 3], "day": [4, 5]}
      )
      sdf = psdf.to_spark()
      self.assertEqual(_get_index_map(sdf), (None, None))
  
      def check(actual, expected):
          actual_scols, actual_labels = actual
          expected_column_names, expected_labels = expected
          self.assertEqual(
              len(actual_scols), len(expected_column_names)
          )
          for actual_scol, expected_column_name in zip(
              actual_scols, expected_column_names
          ):
              expected_scol = sdf[expected_column_name]
              self.assertTrue(
                  spark_column_equals(actual_scol, expected_scol)
              )
          self.assertEqual(actual_labels, expected_labels)
  
      check(_get_index_map(sdf, "year"), (["year"], [("year",)]))
      check(
          _get_index_map(sdf, ["year", "month"]),
          (["year", "month"], [("year",), ("month",)]),
      )
  
      self.assertRaises(
          KeyError, lambda: _get_index_map(sdf, ["year", "hour"])
      )
  
imports: import itertools
  import inspect
  import pandas
  import numpy
  from pyspark import pandas
  from pyspark.pandas.exceptions import PandasNotImplementedError
  from pyspark.pandas.namespace import _get_index_map, read_delta
  from pyspark.pandas.utils import spark_column_equals
  from pyspark.pandas.missing.general_functions import MissingPandasLikeGeneralFunctions
  from pyspark.testing.pandasutils import PandasOnSparkTestCase
  from pyspark.testing.sqlutils import SQLTestUtils
label_desc: Use image node_id 10 for calling the NamespaceTestsMixin obj's underlying member method code with example usage: obj.test_get_index_map() without return types